Casting actors
Physical similarity with the role (or assumptions about the role) has long been a significant factor in casting actors for roles in theatrical (opera, staged plays, ballet, performance art of other sorts) and recorded media (radioplays, TV, film) performances.
While this is a significant issue for all sorts of actors, race-based casting has had a specific and peculiar history in the US, and consequently race-blind casting has emerged as one response to racism within theater and performance art. In race-blind casting, casting is done specifically in disregard of race. Occasionally works are produced in a deliberate effort to do transracial casting as a form of activism.
Similarly, gender-neutral casting attempts to cast actors for roles regardless of gender. Gender-neutral casting has been rarer and has had less penetration into theater generally. However, a small number of all-female or mostly female acting troupes (e.g., Footsteps Theatre in Chicago; the San Francisco-based ?? troupe; another in New York at one time) have set up all-female or mostly-female productions of traditionally staged works (and also highlighted works with great female parts, plays written by women, created opportunities for female stagecraft, direction, and production, etc.).
Race-blind or conscious race-reversal casting may work with, or sometimes against, other efforts to increase media diversity and combat racism within media. In general, live theatrical and performance arts (theater, opera) have been more successful than recorded media with experiments in race- and even gender-neutral casting. Opera, because of a significant focus on vocal qualities, has made even greater progress in race-neutral casting and casting against age and other physical appearance issues. (Vocal type specifications and limitations make cross-gender casting rarer but not unheard-of.)
Recorded media -- film and TV -- have been largely controlled by modes of production, and in capitalist corporate media works, have therefore tended toward the young, beautiful, and white. Thus, increasing the quantity, quality, and overall diversity of media representations of people of color has been a central focus of media diversity work. In the United States, these efforts have been crippled since the 1970s by the anti-affirmative action backlash and by the peculiar structure of government regulation of TV and radio. In many other countries around the world, however, governments take a more active role in ensuring "public interest" programming and can consider diversity issues in their programming. In most countries, this has led to greater media diversity on TV than in the US, although in some countries, such as apartheid South Africa, it has predictably led to censorship and racism.